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Increasing accessibility and reactivity of paper grade pulp by enzymatic treatment for use as dissolving pulp
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
2008 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 23, no 4, 363-368 p.Article in journal (Refereed) Published
Abstract [en]

 In this study, the feasibility of using different kraft pulps as dissolving pulps for the viscose process was investigated. Two different bleached hardwood kraft pulps from eucalypt (Eucalyptus globulus) and birch (Betula pendula) were subjected to several enzymatic and chemical pretreatments in order to improve the accessibility and reactivity of the pulps and to reduce the hemicellulose content. Enzymatic treatments were carried out using a commercial monocomponent endoglucanase and a commercial xylanase. Chemical treatment consisted of an alkali extraction. The effects of these pretreatments on reactivity and viscosity were assayed. In both pulps, the endoglucanase enhanced the cellulose reactivity and reduced the viscosity. The sequential combination of xylanase and endoglucanase enhanced the positive effect of endoglucanase treatment alone for eucalypt but showed no major effect for birch. The addition of an alkali extraction step after the xylanase followed by endoglucanase treatment as a final step significantly reduced the hemicellulose content to 24% while the reactivity reached the value of a commercial dissolving pulp (65-70%). The viscosity, on the other hand, showed a considerably decrease.

Place, publisher, year, edition, pages
2008. Vol. 23, no 4, 363-368 p.
Keyword [en]
Hardwood, Kraft pulp, Dissolving pulp, Reactivity, Xylanase, Monocomponent endoglucanase, Alkali extraction
National Category
Wood Science
Identifiers
URN: urn:nbn:se:kth:diva-8614DOI: 10.3183/NPPRJ-2008-23-04-p363-368ISI: 000262102700002Scopus ID: 2-s2.0-58149242427OAI: oai:DiVA.org:kth-8614DiVA: diva2:13983
Note
QC 20100917. Uppdaterad från Manuskript till Artikel (20100917).Available from: 2008-06-03 Created: 2008-06-03 Last updated: 2012-03-20Bibliographically approved
In thesis
1. Improvement on cellulose accessibility and reactivity of different wood pulps
Open this publication in new window or tab >>Improvement on cellulose accessibility and reactivity of different wood pulps
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [sv]

Cellulosans tillgänglighet och reaktivitet är nyckelparametrar vid framställning av regenererad cellulosa och cellulosaderivat. Det är välkänt att på grund av cellulosans kristallina struktur är tillgängligheten begränsad för lösningsmedel och olika reagens. Till exempel kan en inhomogen substitution av hydroxylgrupperna i cellulosakedjan resultera i cellulosaderivat av sämre kvalitet. Baserat på detta har en del av arbetet i denna studie fokuserat på att förbättra cellulosans tillgänglighet och reaktivitet genom att studera effekten av olika enzymatiska behandlingar med monokomponent endoglukanaser. Resultaten visar att närvaron av en cellulosabindande domän fyller en viktig funktion för att öka cellulosans reaktivitet, men strukturen för den katalytiska domänen visade sig ha den största inverkan på cellulosans tillgänglighet. I kompletterande studier har även effekten av en mekanisk förbehandling i kombination med enzymatisk behandling utvärderats. Kombinationen av förbehandlingarna resulterade i en positiv effekt, cellulosans reaktivitet kunde ökas i större omfattning.

I dag används huvudsakligen dissolvingmassor som råvara vid framställning av cellulosaregenerat och cellulosaderivat. Kraven för dessa s.k. specialmassor är högt cellulosainnehåll samt lågt hemicellulosa- respektive lignininnehåll. På grund av dessa specifika krav är produktionskostnaderna för dessa massor högre än konventionella sulfatmassor. Den andra delen av studien har därför fokuserat på möjligheten att använda dessa sulfatmassor som dissolvingmassa. Det har visats att kombinationen av enzymatiska behandlingar med monokomponent endoglukanas och xylanas följt av ett alkaliskt steg kan resultera i massor där kraven uppfylls med avseende på cellulosans reaktivitet, och cellulosa- respektive hemicellulosainnehåll.

Abstract [en]

The accessibility and reactivity of cellulose are key parameters on the manufacturing of cellulose derivatives and regenerated cellulose. It is well known that, due to the crystalline structure of cellulose, the accessibility of solvents and reagents is limited. For instance, an inhomogeneous substitution of the hydroxyl groups of the cellulose chain might lead to the production of derivatives of low quality. As a consequence, part of this work has focused on improving the accessibility and reactivity on cellulose by studying the effect of different monocomponent endoglucanases. It has been demonstrated that the presence of the cellulose-binding domain plays an important role on the enhancement of cellulose reactivity; however, the structure of the catalytic domain has been showed to have the highest influence on this parameter. Furthermore, the influence of mechanical treatment prior to enzymatic treatment has been examined. The combination of pretreatments showed a positive effect enhancing to a larger extent the cellulose reactivity.

Currently, dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. The requirements for these so-called “special pulps” are a high cellulose content and a low hemicelluloses and lignin content. As a result of these specific demands, the production costs of these pulps are higher than those of common kraft pulps. The second part of this work, therefore, has been focused on the study on the viability of converting kraft pulps into dissolving pulps. It has been demonstrated that the combination of enzymatic treatments using a monocomponent endoglucanase and a xylanase together with the addition of an alkaline step could fulfil the requirements of a commercial dissolving pulp in terms of cellulose reactivity and cellulose and hemicellulose content.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 27 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:43
Keyword
cellulose, accessibility, reactivity, enzymatic treatment, mechanical treatment, chemical treatment, dissolving pulp, paper grade pulps
National Category
Wood Science
Identifiers
urn:nbn:se:kth:diva-4792 (URN)978-91-7178-985-3 (ISBN)
Presentation
2008-06-05, STFI-salen, STFI-Packfors., KTH, Drottning Kristinas väg 61, Stockholm, 14:00
Supervisors
Note
QC 20101117Available from: 2008-06-03 Created: 2008-06-03 Last updated: 2010-11-17Bibliographically approved
2. Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps
Open this publication in new window or tab >>Conversion of Wood and Non-wood Paper-grade Pulps to Dissolving-grade Pulps
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Dissolving-grade pulps are commonly used for the production of cellulose derivatives and regenerated cellulose. To obtain products of high quality, these so-called "special" pulps must fulfill certain requirements, such as high cellulose content, low hemicellulose content, a uniform molecular weight distribution and high cellulose reactivity. Most, if not all, of the commercial dissolving pulps accomplish these demands to a certain extent. Nevertheless, achieving high cellulose accessibility as well as solvent and reagent reactivity is not an easy task due to the compact and complex structure presented by the cellulose.

In the first part of this work, three commercial monocomponent endoglucanases were investigated with the purpose of enhancing the cellulose accessibility and reactivity of a hardwood dissolving pulp. A monocomponent endoglucanase with a cellulose-binding domain (CBD) was shown to significantly improve the cellulose reactivity. The positive effect of this enzyme on dissolving-grade pulps was also observed on paper-grade pulps.

The main focus of the forest industry is the production of paper-grade pulps. Paper-grade pulps are mostly produced by the kraft process. In contrast, dissolving-grade pulps are produced by the sulfite and prehydrolysis kraft processes due to the high purity required for these pulps. The kraft process is known for being the most efficient process in terms of energy and chemical recovery, which makes the production costs of paper-grade pulps lower than those of sulfite dissolving-grade pulps. Besides, the production of dissolving pulps present, among others, higher capital and chemical costs than paper-grade pulps.

Therefore, the viability of converting paper-grade pulps into dissolving pulps is brought into a question. However, this task is not simple because paper-grade pulps contain a lower cellulose content and a higher hemicellulose content than dissolving pulps. They also present lower cellulose reactivity and an inhomogeneous molecular weight distribution. As a consequence, the second part of this work focused on the study of the feasibility of converting kraft pulps into dissolving pulps. Several sequences of treatments of hardwoods and non-wood pulps were investigated. The best sequence for each suitable pulp was developed, and the parameters involved were optimized. After several attempts, it was demonstrated that pulps from birch, eucalypt and sisal fulfill the requirements of a commercial dissolving pulp for the viscose process after being subjected to a sequence of treatments that included two commercial enzymes, a xylanase and a monocomponent endoglucanase, and alkali extraction steps.

 

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. 57 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:46
National Category
Wood Science
Identifiers
urn:nbn:se:kth:diva-26967 (URN)978-91-7415-777-2 (ISBN)
Public defence
2010-12-03, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20101201Available from: 2010-12-01 Created: 2010-11-30 Last updated: 2010-12-01Bibliographically approved

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